Wood veneers and other composite laminates made from natural materials have grown increasingly popular in an effort to balance aesthetic qualities with functionality. For instance, functional as well as aesthetically pleasing articles such as headliners, furniture and other home accessories are made from laminates of wood veneer. As wood is susceptible to a wide range of natural variations in color, grain size, grain direction, humidity content and the like, single layer wood veneers warp and/or twist due to the anisotropy of the natural grain of the wood. For specific applications requiring a thicker wood veneer, multiple layers of wood veneer are glued together to form a wood laminate. However, if the grain of each of the veneer layers is oriented in the same direction, the multi-layer veneer laminate will warp in the same fashion as a single layer veneer. In addition, excessive warpage will cause the wood layers to delaminate. Therefore, in multi-layer laminates of wood veneers, the veneer layers are staged in alternating "with-grain" and "cross-grain" directions in order to minimize warpage of the finished laminate. However, to properly orient the "cross-grain" layers so as to effectively limit warpage necessitates a costly and labor-intensive "stitching" step. Without the "stitching" step, the finished laminate will exhibit unacceptably high warping or twisting.
Moreover, in order to securely bond rigid wood laminates of more substantial cross-sections requires high pressures and high temperatures in order to ensure that the adhesive between the laminate layers cures properly. This process is however highly energy intensive and requires a longer cycle time to facilitate full heat penetration of the laminate through the cross-section. This longer cycle time results in lower productivity, and under-utilization of capital equipment. Accordingly, to produce a given production volume, additional capital outlays are necessitated, such as tooling and equipment costs.
Another problem inherent to the longer cycle times of conventional processes is the pre-curing of the batch adhesive. Longer cycle times create another problem associated with the batch adhesive pre-curing prior to the end of the production run.
Lastly, the use of adhesives in formable composite laminates not only increases cost, and quality issues if the adhesive is not properly cured, but further raises environmental hazards.
Another method to increase the thickness of a wood veneer is to laminate a thin veneer to a more substantial substrate of a different material, such as a plastic sheet. However, differences in the coefficient of thermal expansion between wood and plastic resins causes unacceptable delamination.
Accordingly, there is a need for a formable composite laminate that is durable enough to function effectively over a wide range of applications and yet eliminate the need for a composite adhesive and the problems associated therewith.